Embedded devices such as air conditioners and home electrical appliances accelerate to have multifunctionality. Then, it is difficult to operate, in a conventional way, such an embedded device only using a combination of a plurality of buttons and a liquid crystal display (such as a segment liquid crystal display) which displays fixed content directly relating to the buttons.
Therefore, electric apparatuses employing display devices which use general liquid crystal (so-called full-dot liquid crystal) and which includes so-called graphical user interfaces (GUIs) have been fabricated. As the GUIs, arbitrary diagrams and images are displayed in a liquid crystal screen, and multifunctionality and usability are supported by a method of switching screen displays in the liquid crystal screen from one to another or a method of adding display of a small window used for explanation in the screen. Therefore, users can easily use functions of electric devices, and accordingly, operability is improved.
However, in the display device of these electric devices, content to be displayed in a liquid crystal display and an operation device have considerable restrictions from the viewpoint of fabrication cost.
Considering cost, heat generation, and power consumption, a microcomputer used in an embedded device has low processing performance compared with that in a personal computer. As for a performance ratio thereof, a speed is 1/100 or lower compared to the microcomputer of the personal computer and a storage capacity is 1/1000 or lower of the microcomputer of the personal computer in most cases.
Since the full dot liquid crystal described above realizes display having a high degree of freedom by combining small luminous points, the full dot liquid crystal requires a number of instructions in order to display a single diagram. When a diagram of 1 cm square is to be rendered, for example, approximately a hundred of small luminous points should be changed, and accordingly, approximately a thousand instructions are required.
Most of the processing power of the microcomputer is consumed to realize a GUI process of combining such display diagrams with one another and frequently performing rendering by changing display screens from one to another, and furthermore, most of the storage capacity is consumed to perform intermediate information processing. Therefore, execution of a control application program which realizes an original function of the embedded device may be delayed. As a result, it becomes difficult to design the control application program, and accordingly, it is possible that the number of developing processes is increased.
To address this problem, an apparatus including dedicated hardware (graphic accelerator) used to execute part of the GUI process has been proposed (refer to Patent Literature 1, for example).